Electronic waste

Electronic waste, e-waste, e-scrap, or Waste Electrical and Electronic Equipment (WEEE) describes loosely discarded, surplus, obsolete, or broken electrical or electronic devices. Environmental groups claim that the informal processing of electronic waste in developing countries causes serious health and pollution problems. Some electronic scrap components, such as CRTs, contain contaminants such as lead, cadmium, beryllium, mercury, and brominated flame retardants (Dell XPS M1210 Battery) .

Activists claim that even in developed countries recycling and disposal of e-waste may involve significant risk to workers and communities and great care must be taken to avoid unsafe exposure in recycling operations and leaching of material such as heavy metals from landfills and incineratorashes. Scrap industry and USA EPA officials agree that materials should be managed with caution, but that environmental dangers of unused electronics have been exaggerated by groups which benefit from increased regulation (Dell Studio XPS 1340 Battery) .

Definitions

"Electronic waste" may be defined as all secondary computers, entertainment device electronics, mobile phones, and other items such as television sets and refrigerators, whether sold, donated, or discarded by their original owners. This definition includes used electronics which are destined for reuse, resale, salvage, recycling, or disposal (Dell Studio XPS 1640 Battery) .

Others define the re-usables (working and repairable electronics) and secondary scrap (copper, steel, plastic, etc.) to be "commodities", and reserve the term "waste" for residue or material which was represented as working or repairable but which is dumped or disposed or discarded by the buyer rather than recycled, including residue from reuse and recycling operations (Dell Vostro 1710 Battery) .

Because loads of surplus electronics are frequently commingled (good, recyclable, and non-recyclable), several public policy advocates apply the term "e-waste" broadly to all surplus electronics. The United States Environmental Protection Agency (EPA) includes discarded CRT monitors in its category of "hazardous household waste" (ASUS EEE PC900 battery) .

but considers CRTs set aside for testing to be commodities if they are not discarded, speculatively accumulated, or left unprotected from weather and other damage.

Debate continues over the distinction between "commodity" and "waste" electronics definitions. Some exporters may deliberately leave difficult-to-spot obsolete or non-working equipment mixed in loads of working equipment (through ignorance, or to avoid more costly treatment processes) (Dell RM791 battery) .

Protectionists may broaden the definition of "waste" electronics. The high value of the computer recyclingsubset of electronic waste (working and reusable laptops, computers, and components like RAM) can help pay the cost of transportation for a large number of worthless "electronic commodities" (Sony VGP-BPS13 battery) .

Problems

Rapid change in technology, low initial cost, and planned obsolescence have resulted in a fast-growing surplus of electronic waste around the globe. Dave Kruch, CEO of Cash For Laptops, regards electronic waste as a "rapidly expanding" issue. Technical solutions are available, but in most cases a legal framework, a collection system, logistics, and other services need to be implemented before a technical solution can be applied (Sony VGP-BPL9 battery) .

An estimated 50 million tons of E-waste is produced each year . The USA discards 30 million computers each year and 100 million phones are disposed of in Europe each year. The Environmental Protection Agency estimates that only 15-20% of e-waste is recycled, the rest of these electronics go directly into landfills and incinerators. In the United States, an estimated 70% of heavy metals in landfills comes from discarded electronics (Sony VGP-BPL11 battery) .

Global trade issues

Electronic waste is often exported to developing countries.

4.5-Volt, D, C, AA, AAA, 9-Volt,SR41/AG3, SR44/AG13 cells are all recyclable in most countries.

Increased regulation of electronic waste and concern over the environmental harm which can result from toxic electronic waste has raised disposal costs. The regulation creates an economic disincentive to remove residues prior to export (Sony VGP-BPL15 battery) .

Critics of trade in used electronics maintain that it is too easy for brokers calling themselves recyclers to export unscreened electronic waste to developing countries, such as China, India and parts of Africa, thus avoiding the expense of removing items like bad cathode ray tubes (the processing of which is expensive and difficult). The developing countries are becoming big dump yards of e-waste due to their weak laws (Dell Inspiron E1505 battery) .

Proponents of international trade point to the success of fair trade programs in other industries, where cooperation has led creation of sustainable jobs, and can bring affordable technology in countries where repair and reuse rates are higher.

Defenders of the trade in used electronics say that extraction of metals from virgin mining has also been shifted to developing countries (Dell Latitude E6400 battery) .

Hard-rock mining of copper, silver, gold and other materials extracted from electronics is considered far more environmentally damaging than the recycling of those materials. They also state that repair and reuse of computers and televisions has become a "lost art" in wealthier nations, and that refurbishing has traditionally been a path to development (HP Pavilion dv6000 Battery) .

South Korea, Taiwan, and southern China all excelled in finding "retained value" in used goods, and in some cases have set up billion-dollar industries in refurbishing used ink cartridges, single-use cameras, and working CRTs. Refurbishing has traditionally been a threat to established manufacturing, and simple protectionism explains some criticism of the trade (Sony Vaio VGN-FZ31S battery) .

Works like "The Waste Makers" by Vance Packard explain some of the criticism of exports of working product, for example the ban on import of tested working Pentium 4 laptops to China, or the bans on export of used surplus working electronics by Japan.

Opponents of surplus electronics exports argue that lower environmental and labor standards, cheap labor, and the relatively high value of recovered raw materials leads to a transfer of pollution-generating activities, such as burning of copper wire . In China, Malaysia, India, Kenya, and various African countries, electronic waste is being sent to these countries for processing, s (Sony Vaio VGN-FZ31S battery) .

ometimes illegally. Many surplus laptops are routed to developing nations as "dumping grounds for e-waste". Because the United States has not ratified the Basel Convention or its Ban Amendment, and has no domestic laws forbidding the export of toxic waste, the Basel Action Network estimates that about 80% of the electronic waste directed to recycling in the U.S. does not get recycled there at all, but is put on container ships and sent to countries such as China (Hp pavilion dv6000 battery) .

This figure is disputed as an exaggeration by the EPA, the Institute for Scrap Recycling Industries, and the World Reuse, Repair and Recycling Association. Independent research by Arizona State University showed that 87-88% of imported used computers had a higher value than the best value of the constituent materials they contained, and that "the official trade in end-of-life computers is thus drive by reuse as opposed to recycling (Sony VGN-FW11S Battery) ."

Guiyu in the Shantou region of China, Delhi and Bangalore in India as well as the Agbogbloshie site near Accra, Ghana have electronic waste processing areas. Uncontrolled burning, disassembly, and disposal can cause a variety of environmental problems such as groundwater contamination, atmospheric pollution, or even water pollution either by immediate discharge or due tosurface runoff (especially near coastal areas), as well as health problems including occupational safety and health effects among those directly involved, due to the methods of processing the waste (Sony VGP-BPS13A/B Battery) .

Thousands of men, women, and children are employed in highly polluting, primitive recycling technologies, extracting the metals, toners, and plastics from computers and other electronic waste. Recent studies show that 7 out of 10 children in this region have too much lead in their blood (Sony VGP-BPS13B/B Battery) .

Proponents of the trade say growth of internet access is a stronger correlation to trade than poverty. Haiti is poor and closer to the port of New York than southeast Asia, but far more electronic waste is exported from New York to Asia than to Haiti. Thousands of men, women, and children are employed in reuse, refurbishing, repair, and remanufacturing, sustainable industries in decline in developed countries. It is held that denying developing nations access to used electronics denies them affordable products and internet access (Toshiba Satellite P10 Battery) .

Opponents of the trade argue that developing countries utilize methods that are more harmful and more wasteful. An expedient and prevalent method is simply to toss equipment onto an open fire, in order to melt plastics and to burn away unvaluable metals. This releases carcinogens and neurotoxins into the air, contributing to an acrid, lingering smog. These noxious fumes include dioxins andfurans. Bonfire refuse can be disposed of quickly into drainage ditches or waterways feeding the ocean or local water supplies (SONY VAIO VGN-FZ210CE Battery) .

In June 2008, a container of electronic waste, destined from the Port of Oakland in the U.S. to Sanshui District in mainland China, was intercepted in Hong Kong by Greenpeace. Concern over exports of electronic waste were raised in press reports in India,Ghana, Ivory Coast, and Nigeria (SONY VAIO VGN-FZ38M Battery) .

E-waste management

Recycling

Computer monitors are typically packed into low stacks on wooden pallets forrecycling and then shrink-wrapped.

See also: Computer recycling

Today the electronic waste recycling business is in all areas of the developed world a large and rapidly consolidating business (SONY VAIO VGN-FZ31z Battery) .

Electronic waste processing systems have matured in recent years, following increased regulatory, public, and commercial scrutiny, and a commensurate increase in entrepreneurial interest. Part of this evolution has involved greater diversion of electronic waste from energy-intensive downcycling processes (e.g., conventional recycling), where equipment is reverted to a raw material form (SONY VAIO VGN-FZ31E Battery) .

This diversion is achieved through reuse and refurbishing. The environmental and social benefits of reuse include diminished demand for new products and virgin raw materials (with their own environmental issues); larger quantities of pure water and electricity for associated manufacturing; less packaging per unit; availability of technology to wider swaths of society due to greater affordability of products; and diminished use of landfills (SONY VAIO VGN-FZ31J Battery) .

Audiovisual components, televisions, VCRs, stereo equipment, mobile phones, other handheld devices, and computer components contain valuable elements and substances suitable for reclamation, including lead, copper, and gold.

One of the major challenges is recycling the printed circuit boards from the electronic wastes (SONY VAIO VGN-FZ31M Battery) .

The circuit boards contain such precious metals as gold, silver, platinum, etc. and such base metals as copper, iron, aluminum, etc. Conventional method employed is mechanical shredding and separation but the recycling efficiency is low. Alternative methods such as cryogenic decomposition have been studied for printed circuit board recycling, and some other methods are still under investigation (SONY VAIO VGN-FZ31B Battery) .

Consumer awareness efforts

• AddressTheMess.com is a Comedy Central pro-social campaign that seeks to increase awareness of the dangers of electronic waste and to encourage recycling. Partners in the effort include Earth911.org, ECOInternational.com, and the U.S. Environmental Protection Agency (SONY VGP-BPS13 Battery) ?. Many Comedy Central viewers are early adopters of new electronics, and produce a commensurate amount of waste that can be directed towards recycling efforts. The station is also taking steps to reduce its own environmental impact, in partnership with NativeEnergy.com, a company that specializes in renewable energy and carbon offsets (Dell Precision M70 Battery) .
• The Electronics TakeBack Coalition is a campaign aimed at protecting human health and limiting environmental effects where electronics are being produced, used, and discarded. The ETBC aims to place responsibility for disposal of technology products on electronic manufacturers and brand owners, primarily through community promotions and legal enforcement initiatives (Acer Aspire One battery) . It provides recommendations for consumer recycling and a list of recyclers judged environmentally responsible.
• The grassroots Silicon Valley Toxics Coalition (svtc.org) focuses on promoting human health and addresses environmental justice problems resulting from toxins in technologies.
• Basel Action Network (BAN.org) is uniquely focused on addressing global environmental injustices and economic inefficiency of global "toxic trade" (Toshiba Satellite L305 Battery) . It works for human rights and the environment by preventing disproportionate dumping on a large scale. It promotes sustainable solutions and attempts to ban waste trade.
• Texas Campaign for the Environment (texasenvironment.org) works to build grassroots support for e-waste recycling and uses community organizing to pressure electronics manufacturers and elected officials to enact producer takeback recycling policies and commit to responsible recycling programs (Toshiba Satellite M65 battery) .
• The World Reuse, Repair, and Recycling Association (wr3a.org) is an organization dedicated to improving the quality of exported electronics, encouraging better recycling standards in importing countries, and improving practices through "Fair Trade" principles.
• Take Back My TV is a project of The Electronics TakeBack Coalition and grades television manufacturers to find out which are responsible and which are not (Toshiba Satellite T4900 Battery) .

Processing techniques

Recycling the lead from batteries.

In developed countries, electronic waste processing usually first involves dismantling the equipment into various parts (metal frames, power supplies, circuit boards, plastics), often by hand. The advantages of this process are the human's ability to recognize and save working and repairable parts, including chips, transistors, RAM, etc. The disadvantage is that the labor is often cheapest in countries with the lowest health and safety standards (Toshiba PA3399U-2BRS battery) .

In an alternative bulk system, a hopper conveys material for shredding into a sophisticated mechanical separator, with screening and granulating machines to separate constituent metal and plastic fractions, which are sold to smelters or plastics recyclers. Such recycling machinery is enclosed and employs a dust collection system. Most of the emissions are caught by scrubbers and screens (Dell Latitude E6400 battery) .

Magnets, eddy currents, and trommel screens are employed to separate glass, plastic, and ferrous and nonferrous metals, which can then be further separated at a smelter. Leaded glass from CRTs is reused in car batteries, ammunition, and lead wheel weights, or sold to foundries as a fluxing agent in processing raw lead ore. Copper, gold, palladium, silver, and tin are valuable metals sold to smelters for recycling. Hazardous smoke and gases are captured, contained, and treated to mitigate environmental threat (Toshiba Satellite A200 Battery) .

These methods allow for safe reclamation of all valuable computer construction materials. Hewlett-Packard product recycling solutions manager Renee St. Denis describes its process as: "We move them through giant shredders about 30 feet tall and it shreds everything into pieces about the size of a quarter. Once your disk drive is shredded into pieces about this big, it's hard to get the data off (Toshiba Satellite 1200 Battery) ."

An ideal electronic waste recycling plant combines dismantling for component recovery with increased cost-effective processing of bulk electronic waste.

Reuse is an option to recycling because it extends the lifespan of a device. Devices still need eventual recycling, but by allowing others to purchase used electronics, recycling can be postponed and value gained from device use (Toshiba NB100 Battery) .

Benefits of Recycling

Recycling raw materials from end-of-life electronics is the most effective solution to the growing e-waste problem. Most electronic devices contain a variety of materials, including metals that can be recovered for future uses. By dismantling and providing reuse possibilities, intact natural resources are conserved and air and water pollution caused by hazardous disposal is avoided (Toshiba Satellite M300 Battery) .

Additionally, recycling reduces the amount of greenhouse gas emissions caused by the manufacturing of new products. It simply makes good sense and is efficient to recycle and to do our part to keep the environment green.

Electronic waste substances

Several sizes of button and coin cell with 2 9v batteries as a size comparison (Dell INSPIRON 1525 battery) .

Enlarge to see the button and coin cells’ size code markings. They are all recyclable in both the UK andIreland since they contain toxic metals like lead, mercury and cadmium.

Some computer components can be reused in assembling new computer products, while others are reduced to metals that can be reused in applications as varied as construction, flatware, and jewelry (Dell Inspiron Mini 10 Battery) .

Substances found in large quantities include epoxy resins, fiberglass, PCBs, PVC (polyvinyl chlorides), thermosetting plastics, lead, tin, copper, silicon,beryllium, carbon, iron and aluminium.

Elements found in small amounts include cadmium, mercury, and thallium.

Elements found in trace amounts include americium, antimony, arsenic, barium, bismuth, boron, cobalt, europium, gallium, germanium, gold, indium, lithium,manganese, nickel, niobium, palladium, platinum, rhodium, ruthenium, selenium, silver, tantalum, terbium, thorium, titanium, vanadium, and yttrium (Dell Latitude D830 Battery) .

Almost all electronics contain lead and tin (as solder) and copper (as wire and printed circuit board tracks), though the use of lead-free solder is now spreading rapidly. The following are ordinary applications:

Hazardous

• Americium: smoke alarms (radioactive source) (Dell Studio 1735 Battery) .
• Mercury: fluorescent tubes (numerous applications), tilt switches (pinball games, mechanical doorbells, thermostats). There are no liquid mercury switches in ordinary computers, and the elimination of mercury batteries in many new-model computers is taking place.
• Sulphur: lead-acid batteries.
• PCBs: prior to ban, almost all 1930s–1970s equipment, including capacitors, transformers, wiring insulation, paints, inks, and flexible sealants (Dell Latitude D620 Battery) .
• PBBs: used after the ban to replace PCBs. Also used as flame retardant.
• Cadmium: light-sensitive resistors, corrosion-resistant alloys for marine and aviation environments, nickel-cadmium batteries.
• Lead: solder, CRT monitor glass, lead-acid batteries, some formulations of PVC. A typical 15-inch cathode ray tube may contain 1.5 pounds of lead, but other CRTs have been estimated as having up to 8 pounds of lead (SONY VAIO VGN-FZ150E Battery) .
• Beryllium oxide: filler in some thermal interface materials such as thermal grease used on heatsinks for CPUs and power transistors, magnetrons, X-ray-transparent ceramic windows, heat transfer fins in vacuum tubes, and gas lasers.
• Polyvinyl chloride Third most widely produced plastic, contains additional chemicals to change the chemical consistency of the product (Dell Studio 1555 Battery) . Some of these additional chemicals called additives can leach out of vinyl products. Plasticizers that must be added to make PVC flexible have been additives of particular concern

Generally non-hazardous

• Tin: solder, coatings on component leads.
• Copper: copper wire, printed circuit board tracks, component leads (Dell Latitude D610 Battery) .
• Aluminium: nearly all electronic goods using more than a few watts of power (heatsinks), electrolytic capacitors.
• Iron: steel chassis, cases, and fixings.
• Germanium: 1950s–1960s transistorized electronics (bipolar junction transistors).
• Silicon: glass, transistors, ICs, printed circuit boards (Dell Inspiron 300M Battery) .
• Nickel: nickel-cadmium batteries.
• Lithium: lithium-ion batteries.
• Zinc: plating for steel parts.
• Gold: connector plating, primarily in computer equipment (Dell RM791 battery) .

BIOS

In IBM PC Compatible computers, the basic input/output system (BIOS), also known as the System BIOS, is a de facto standard defining a firmware interface.

Phoenix AwardBIOS CMOS (non-volatile memory) Setup utility on a standard PC

The BIOS of a PC software is built into the PC, and is the first code run by a PC when powered on ('boot firmware') (Dell XPS M1210 Battery) .

The primary function of the BIOS is to load and start an operating system. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware. The BIOS then locates software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD, and loads and executes that software, giving it control of the PC (Dell Studio XPS 1340 Battery) .

This process is known as booting, or booting up, which is short for bootstrapping.

BIOS software is stored on a non-volatile ROM chip built into the system on the mother board. The BIOS software is specifically designed to work with the particular type of system in question, including having a knowledge of the workings of various devices that make up the complementary chipset of the system (Dell Studio XPS 1640 Battery) .

In modern computer systems, the BIOS chip's contents can be rewritten allowing BIOS software to be upgraded.

A BIOS will also have a user interface (or UI for short). Typically this is a menu system accessed by pressing a certain key on the keyboard when the PC starts. In the BIOS UI, a user can (Dell Vostro 1710 Battery) :

• configure hardware
• set the system clock
• enable or disable system components
• select which devices are eligible to be a potential boot device (ASUS EEE PC900 battery)
• set various password prompts, such as a password for securing access to the BIOS UI functions itself and preventing malicious users from booting the system from unauthorized peripheral devices.

The BIOS provides a small library of basic input/output functions used to operate and control the peripherals such as the keyboard, text display functions and so forth, and these software library functions are callable by external software (Dell RM791 battery) .

In the IBM PC and AT, certain peripheral cards such as hard-drive controllers and video display adapters carried their own BIOS extension ROM, which provided additional functionality. Operating systems and executive software, designed to supersede this basic firmware functionality, will provide replacement software interfaces to applications (Sony VGP-BPS13 battery) .

The role of the BIOS has changed over time; today BIOS is a legacy system, superseded by the more complex Extensible Firmware Interface (EFI), but BIOS remains in widespread use, and EFI booting has only been supported in x86 Windows since 2008. BIOS is primarily associated with the 16-bit and 32-bit architecture eras (x86-32), while EFI is used for some 32-bit and most 64-bit architectures (Sony VGP-BPL9 battery) .

Today BIOS is primarily used for booting a system, and for certain additional features such as power management (ACPI) and video initialization (in X.org), but otherwise is not used during the ordinary running of a system, while in early systems (particularly in the 16-bit era), BIOS was used for hardware access – operating systems (notably MS-DOS) would call the BIOS rather than directly accessing the hardware (Sony VGP-BPL11 battery) .

In the 32-bit era and later, operating systems instead generally directly accessed the hardware using their own device drivers. However, the distinction between BIOS and EFI is rarely made in terminology by the average computer user, making BIOS a catch-all term for both systems (Sony VGP-BPL15 battery) .

Terminology

The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had only a simple boot loader in their ROM). Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M BIOS (Dell Inspiron E1505 battery) .

Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM were commonly used. Some Sun and PowerPC-based computers use Open Firmware for this purpose. There are a few alternatives for Legacy BIOS in the x86 world: Extensible Firmware Interface, Open Firmware (used on the OLPC XO-1) and coreboot (Dell Latitude E6400 battery) .

IBM PC-compatible BIOS chips

In principle, the BIOS in ROM was customized to the particular manufacturer's hardware, allowing low-level services (such as reading a keystroke or writing a sector of data to diskette) to be provided in a standardized way to the operating system. For example, an IBM PC might have had either a monochrome or a color display adapter, using different display memory addresses and hardware - but the BIOS service to print a character on the screen in text mode would be the same (HP Pavilion dv6000 Battery) .

Prior to the early 1990s, BIOSes were stored in ROM or PROM chips, which could not be altered by users. As its complexity and need for updates grew, and re-programmable parts became more available, BIOS firmware was most commonly stored on EEPROM or flash memory devices (Sony Vaio VGN-FZ31S battery) .

According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOS chips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard erasable PROM (EPROM) chips. EPROM chips may be erased by prolonged exposure to ultraviolet light, which accessed the chip via the window. Chip manufacturers use EPROM programmers (blasters) to program EPROM chips (Sony Vaio VGN-FZ31S battery) .

Electrically erasable (EEPROM) chips come with the additional feature of allowing a BIOS reprogramming via higher-than-normal amounts of voltage. BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes (Hp pavilion dv6000 battery) .

Beginning with the IBM AT, PCs supported a hardware clock settable through BIOS. It had a century bit which allowed for manually changing the century when the year 2000 happened. Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000 by setting the century bit automatically when the clock rolled past midnight, December 31, 1999 (Sony VGN-FW11S Battery) .

The first flash chips were attached to the ISA bus. Starting in 1997, the BIOS flash moved to the LPC bus, a functional replacement for ISA, following a new standard implementation known as "firmware hub" (FWH). In 2006, the first systems supporting a Serial Peripheral Interface (SPI) appeared, and the BIOS flash moved again (Sony VGP-BPS13A/B Battery) .

The size of the BIOS, and the capacities of the ROM, EEPROM and other media it may be stored on, has increased over time as new features have been added to the code; BIOS versions now exist with sizes up to 16 megabytes. Some modern motherboards are including even bigger NAND Flash ROM ICs on board which are capable of storing whole compact operating system distribution like some Linux distributions (Sony VGP-BPS13B/B Battery) .

For example, some recent ASUS motherboards included SplashTop Linux embedded into their NAND Flash ROM ICs.

Flashing the BIOS

In modern PCs the BIOS is stored in rewritable memory, allowing the contents to be replaced or 'rewritten'. This rewriting of the contents is sometimes termed 'flashing'. This is done by a special program, usually provided by the system's manufacturer (Toshiba Satellite P10 Battery) .

A file containing such contents is sometimes termed 'a BIOS image'. A BIOS might be reflashed in order to upgrade to a newer version to fix bugs or provide improved performance or to support newer hardware, or a reflashing operation might be needed to fix a damaged BIOS (SONY VAIO VGN-FZ210CE Battery) .

BIOS chip vulnerabilities

An American Megatrends BIOS registering the “Intel CPU uCode Error” while doing POST, most likely a problem with the POST.

EEPROM chips are advantageous because they can be easily updated by the user; hardware manufacturers frequently issue BIOS updates to upgrade their products, improve compatibility and remove bugs (SONY VAIO VGN-FZ38M Battery) .

However, this advantage had the risk that an improperly executed or aborted BIOS update could render the computer or device unusable. To avoid these situations, more recent BIOSes use a "boot block"; a portion of the BIOS which runs first and must be updated separately. This code verifies if the rest of the BIOS is intact (using hash checksums or other methods) before transferring control to it (SONY VAIO VGN-FZ31z Battery) .

If the boot block detects any corruption in the main BIOS, it will typically warn the user that a recovery process must be initiated by booting from removable media (floppy, CD or USB memory) so the user can try flashing the BIOS again. Some motherboards have a backup BIOS (sometimes referred to as DualBIOS boards) to recover from BIOS corruptions (SONY VAIO VGN-FZ31E Battery) .

Overclocking

Some BIOS chips allow overclocking, an action in which the CPU is adjusted to a higher clock rate than its factory preset. Overclocking may, however, seriously compromise system reliability in insufficiently cooled computers and generally shorten component lifespan (SONY VAIO VGN-FZ31J Battery) .

Virus attacks

There are at least three known BIOS attack viruses, two of which were for demonstration purposes.

CIH

The first was a virus which was able to erase Flash ROM BIOS content, rendering computer systems unstable. CIH, also known as "Chernobyl Virus", appeared for the first time in mid-1998 and became active in April 1999 (SONY VAIO VGN-FZ31M Battery) .

It affected systems' BIOS's and often they could not be fixed on their own since they were no longer able to boot at all. To repair this, Flash ROM IC had to be removed from the motherboard to be reprogrammed elsewhere. Damage from CIH was possible since the virus was specifically targeted at the then widespread Intel i430TX motherboard chipset, and the most common operating systems of the time were based on the Windows 9x family allowing direct hardware access to all programs (SONY VAIO VGN-FZ31B Battery) .

Modern systems are not vulnerable to CIH because of a variety of chipsets being used which are incompatible with the Intel i430TX chipset, and also other Flash ROM IC types. There is also extra protection from accidental BIOS rewrites in the form of boot blocks which are protected from accidental overwrite or dual and quad BIOS equipped systems which may, in the event of a crash, use a backup BIOS (SONY VGP-BPS13 Battery) .

Also, all modern operating systems like Linux, Mac OS X, Windows NT-based Windows OS like Windows 2000, Windows XP and newer, do not allow user mode programs to have direct hardware access. As a result, as of 2008, CIH has become essentially harmless, at worst causing annoyance by infecting executable files and triggering alerts from antivirus software. Other BIOS viruses remain possible, however : since most Windows users run all applications with administrative privileges, a modern CIH-like virus could in principle still gain access to hardware (Dell Precision M70 Battery) .

Black Hat 2006

The second one was a technique presented by John Heasman, principal security consultant for UK based Next-Generation Security Software at the Black Hat Security Conference (2006), where he showed how to elevate privileges and read physical memory, using malicious procedures that replaced normal ACPI functions stored in flash memory (Acer Aspire One battery) .

Persistent BIOS Infection

The third one, known as "Persistent BIOS infection", was a method presented in CanSecWest Security Conference (Vancouver, 2009) and SyScan Security Conference (Singapore, 2009) where researchers Anibal Sacco and Alfredo Ortega, from Core Security Technologies, demonstrated insertion of malicious code into the decompression routines in the BIOS, allowing for nearly full control of the PC at every start-up, even before the operating system is booted (Toshiba Satellite L305 Battery) .

The proof-of-concept does not exploit a flaw in the BIOS implementation, but only involves the normal BIOS flashing procedures. Thus, it requires physical access to the machine or for the user on the operating system to be root. Despite this, however, researchers underline the profound implications of their discovery: “We can patch a driver to drop a fully working rootkit. We even have a little code that can remove or disable antivirus (Toshiba Satellite M65 battery) .”

Firmware on adapter cards

A computer system can contain several BIOS firmware chips. The motherboard BIOS typically contains code to access hardware components absolutely necessary for bootstrapping the system, such as the keyboard (either PS/2 or on a USB human interface device), and storage (floppy drives, if available, and IDE or SATA hard disk controllers). In addition, plug-in adapter cards such as SCSI, RAID,Network interface cards, and video boards often include their own BIOS (e.g. Video BIOS), complementing or replacing the system BIOS code for the given component (Toshiba Satellite T4900 Battery) .

(This code is generally referred to as an option ROM.) Even devices built into the motherboard can behave in this way; their option ROMs can be stored as separate code on the main BIOS flash chip, and upgraded either in tandem with, or separately to, the main BIOS.

An add-in card usually only requires an option ROM if it (Toshiba PA3399U-2BRS battery) :

• Needs to be used before the operating system can be loaded (usually this means it is required in the bootstrapping process), and
• Is too sophisticated or specific a device to be handled by the main BIOS

Older PC operating systems, such as MS-DOS (including all DOS-based versions of Microsoft Windows), and early-stage bootloaders, may continue to use the BIOS for input and output (Dell Latitude E6400 battery) .

However, the restrictions of the BIOS environment means that modern OSes will almost always use their own device drivers to directly control the hardware. Generally, these device drivers only use BIOS and option ROM calls for very specific (non-performance-critical) tasks, such as preliminary device initialization (Toshiba Satellite A200 Battery) .

In order to discover memory-mapped option ROMs during the boot process, PC BIOS implementations scan real memory from 0xC0000 to 0xF0000 on 2 KiB boundaries, looking for a ROM signature:0xAA55 (0x55 followed by 0xAA, since the x86 architecture is little-endian). In a valid expansion ROM, this signature is immediately followed by a single byte indicating the number of 512-byte blocks it occupies in real memory (Toshiba Satellite 1200 Battery) .

The next byte contains an offset describing the option ROM's entry point, to which the BIOS immediately transfers control. At this point, the expansion ROM code takes over, using BIOS services to register interrupt vectors for use by post-boot applications, provide a user configuration interface, or display diagnostic information.

There are many methods and utilities for examining the contents of various motherboard BIOS and expansion ROMs, such as Microsoft DEBUG or the UNIX dd (Toshiba NB100 Battery) .

BIOS boot specification

If the expansion ROM wishes to change the way the system boots (such as from a network device or a SCSI adapter for which the BIOS has no driver code), it can use the BIOS Boot Specification(BBS) API to register its ability to do so. Once the expansion ROMs have registered using the BBS APIs, the user can select among the available boot options from within the BIOS's user interface. This is why most BBS compliant PC BIOS implementations will not allow the user to enter the BIOS's user interface until the expansion ROMs have finished executing and registering themselves with the BBS API (Toshiba Satellite M300 Battery) .

Changing role of the BIOS

Some operating systems, for example MS-DOS, rely on the BIOS to carry out most input/output tasks within the PC.A variety of technical reasons makes it inefficient for some recent operating systems written for 32-bit CPUs such as Linux and Microsoft Windows to invoke the BIOS directly. Larger, more powerful, servers and workstations using PowerPC or SPARC CPUs by several manufacturers developed a platform-independent Open Firmware (IEEE-1275), based on the Forth programming language (Dell INSPIRON 1525 battery) .

It is included with Sun's SPARC computers, IBM's RS/6000 line, and other PowerPC CHRP motherboards. Later x86-based personal computer operating systems, like Windows NT, use their own, native drivers which also makes it much easier to extend support to new hardware, while the BIOS still relies on a legacy 16-bit runtime interface (Dell Inspiron Mini 10 Battery) .

There was a similar transition for the Apple Macintosh, where the system software originally relied heavily on the ToolBox—a set of drivers and other useful routines stored in ROM based on Motorola's 680x0 CPUs. These Apple ROMs were replaced by Open Firmware in the PowerPC Macintosh, then EFI in Intel Macintosh computers (Dell Latitude D830 Battery) .

Later BIOS took on more complex functions, by way of interfaces such as ACPI; these functions include power management, hot swapping and thermal management. However BIOS limitations (16-bit processor mode, only 1 MiB addressable space, PC AT hardware dependencies, etc.) were seen as clearly unacceptable for the newer computer platforms. Extensible Firmware Interface (EFI) is a specification which replaces the runtime interface of the legacy BIOS (Dell Studio 1735 Battery) .

Initially written for the Itanium architecture, EFI is now available for x86 and x86-64 platforms; the specification development is driven by The Unified EFI Forum, an industry Special Interest Group.

Linux has supported EFI via the elilo boot loader. The Open Source community increased their effort to develop a replacement for proprietary BIOSes and their future incarnations with an open sourced counterpart through the coreboot and OpenBIOS/Open Firmware projects (Dell Latitude D620 Battery) .

AMD provided product specifications for some chipsets, and Google is sponsoring the project. Motherboard manufacturer Tyanoffers coreboot next to the standard BIOS with their Opteron line of motherboards. MSI and Gigabyte Technology have followed suit with the MSI K9ND MS-9282 and MSI K9SD MS-9185 resp. the M57SLI-S4 models (SONY VAIO VGN-FZ150E Battery) .

Some BIOSes contain a "SLIC", a digital signature placed inside the BIOS by the manufacturer, for example Dell. This SLIC is inserted in the ACPI table and contains no active code. Computer manufacturers that distribute OEM versions of Microsoft Windows and Microsoft application software can use the SLIC to authenticate licensing to the OEM Windows Installation disk and/or systemrecovery disc containing Windows software (Dell Studio 1555 Battery) .

Systems having a SLIC can be activated with an OEM Product Key, and they verify an XML formatted OEM certificate against the SLIC in the BIOS as a means of self-activating. If a user performs a fresh install of Windows, they will need to have possession of both the OEM key and the digital certificate for their SLIC in order to bypass activation; in practice this is extremely unlikely and hence the only real way this can be achieved is if the user performs a restore using a pre-customised image provided by the OEM (Dell Latitude D610 Battery).

The BIOS business

The vast majority of PC motherboard suppliers license a BIOS "core" and toolkit from a commercial third-party, known as an "independent BIOS vendor" or IBV. The motherboard manufacturer then customizes this BIOS to suit its own hardware. For this reason, updated BIOSes are normally obtained directly from the motherboard manufacturer (Dell Latitude E6400 battery) .

Major BIOS vendors include American Megatrends (AMI), Insyde Software, Phoenix Technologies and Byosoft. Former vendors include Award Software which was acquired by Phoenix Technologies in 1998. Phoenix has now phased out the Award Brand name. General Software, which was also acquired by Phoenix in 2007, sold BIOS for Intel processor based embedded systems (Dell Inspiron 300M Battery) .

Advanced Configuration and Power Interface

In computing, the Advanced Configuration and Power Interface (ACPI) specification provides an open standard for unified operating system-centric device configuration and power management. ACPI, first released in December 1996, defines platform-independent interfaces for hardware discovery, configuration, power management and monitoring (Dell Inspiron E1505 battery) .

The specification is central to Operating System-directed configuration and Power Management (OSPM); a term used to describe a system implementing ACPI, which therefore removes device management responsibilities from legacy firmware interfaces. The standard was originally developed by Intel, Microsoft, and Toshiba, and last published as "Revision 4.0a", on April 5, 2010. As of 2010, developers of ACPI also include HP andPhoenix (Dell RM791 battery) .

Overview

ACPI aims to consolidate and improve upon existing power and configuration standards for hardware devices. It provides a transition from existing standards to entirely ACPI-compliant hardware, with some ACPI operating systems already removing support for legacy hardware. With the intention of replacing Advanced Power Management, the MultiProcessor Specification and the Plug and Play BIOS Specification, the standard brings power management into operating system control (OSPM), as opposed to the previous BIOS central system, which relied on platform-specific firmware to determine power management and configuration policy (Dell XPS M1530 battery) .

The ACPI specification contains numerous related components for hardware and software programming, as well as a unified standard for device/power interaction and bus configuration. As a document that unifies many previous standards it covers many areas, for system and device builders as well as system programmers. Some software developers have trouble implementing ACPI and express concerns about the requirements that bytecode from an external source must be run by the system with full privileges (Dell XPS M2010 battery) .

Linus Torvalds, creator of the Linux kernel, once described it as "a complete design disaster in every way", in relation to his view that "modern PCs are horrible".

Microsoft Windows 98 was the first operating system with full support for ACPI, with Windows 2000, Windows XP, Windows Vista, Windows 7, eComStation, FreeBSD, NetBSD,OpenBSD, HP-UX, OpenVMS, Linux and PC versions of SunOS all having at least some support for ACPI (Dell Vostro 1000 battery) .

OSPM responsibilities

ACPI requires that once an OSPM-compatible operating system has activated ACPI on a computer, it then takes over and has exclusive control of all aspects of power management and device configuration. The OSPM implementation must expose an ACPI-compatible environment to device drivers, which exposes certain system, device and processor states (HP Pavilion dv9000 battery) .

Power States

Global states

The ACPI specification defines the following seven states (so-called global states) for an ACPI-compliant computer-system:

• G0 (S0): Working
• G1, Sleeping subdivides into the four states S1 through S4 (Sony Vaio VGN-FZ61B battery)
• S1: All processor caches are flushed, and the CPU(s) stop executing instructions. Power to the CPU(s) and RAM is maintained; devices that do not indicate they must remain on may be powered down.
• S2: CPU powered off
• S3: Commonly referred to as Standby, Sleep, or Suspend to RAM. RAM remains powered
• S4: Hibernation or Suspend to Disk. All content of main memory is saved to non-volatile memory such as a hard drive, and is powered down.

• G2 (S5), Soft Off: G2 is almost the same as G3 Mechanical Off, but some components remain powered so the computer can "wake" from input from the keyboard, clock, modem, LAN, or USBdevice (Sony Vaio VGN-FZ18M battery) .

• G3, Mechanical Off: The computer's power consumption approaches close to zero, to the point that the power cord can be removed and the system is safe for dis-assembly (typically, only the real-time clock is running off its own small battery).

Furthermore, the specification defines a Legacy state: the state on an operating system which does not support ACPI. In this state, the hardware and power are not managed via ACPI, effectively disabling ACPI (Sony VGN-FZ21M battery) .

Device states

The device states D0-D3 are device-dependent:

• D0 Fully-On is the operating state.
• D1 and D2 are intermediate power-states whose definition varies by device.
• D3 Off has the device powered off and unresponsive to its bus (Dell Precision M70 Battery) .

Processor states

The CPU power states C0-C3 are defined as follows:

• C0 is the operating state.
• C1 (often known as Halt) is a state where the processor is not executing instructions, but can return to an executing state essentially instantaneously. All ACPI-conformant processors must support this power state. Some processors, such as the Pentium 4, also support an Enhanced C1 state (C1E or Enhanced Halt State) for lower power consumption (Dell XPS M1210 Battery) .

• C2 (often known as Stop-Clock) is a state where the processor maintains all software-visible state, but may take longer to wake up. This processor state is optional.
• C3 (often known as Sleep) is a state where the processor does not need to keep its cache coherent, but maintains other state. Some processors have variations on the C3 state (Deep Sleep, Deeper Sleep, etc.) that differ in how long it takes to wake the processor. This processor state is optional (Dell Vostro 1400 Battery) .

Performance states

While a device or processor operates (D0 and C0, respectively), it can be in one of several power-performance states. These states are implementation-dependent, but P0 is always the highest-performance state, with P1 to Pn being successively lower-performance states, up to an implementation-specific limit of n no greater than 16 (Dell Vostro 1510 Battery) .

P-states have become known as SpeedStep in Intel processors, as PowerNow! or Cool'n'Quiet in AMD processors, and as PowerSaver in VIA processors.

• P0 max power and frequency
• P1 less than P0, voltage/frequency scaled
• Pn less than P(n-1), voltage/frequency scaled (Dell Vostro 2510 Battery)

Hardware Interface

ACPI-compliant systems interact with hardware through either a "Function Fixed Hardware (FFH) Interface" or a platform-independent hardware programming model which relies on platform-specificAML provided by the original equipment manufacturer (OEM) (Dell Vostro A860 Battery) .

Function Fixed Hardware interfaces are platform-specific features, provided by platform manufacturers for the purposes of performance and failure recovery. Standard Intel-based PCs have a fixed function interface defined by Intel[8], which provides a set of core functionality that reduces an ACPI-compliant system's need for full driver stacks for providing basic functionality during boot time or in the case of major system failure (Dell Vostro A90 Battery) .

Firmware Interface

ACPI defines a large number of tables that provide the interface between an ACPI-compliant operating system and system firmware. These allow description of system hardware in a platform-independent manner, and are presented as either fixed formatted data structures or in ACPI Machine Language (AML). The main AML table is the DSDT (differentiated system description table (HP Pavilion DV4 Battery) .

The Root System Description Pointer is located in a platform-dependent manner, and describes the rest of the tables.

ACPI Component Architecture (ACPICA)

The ACPI Component Architecture (ACPICA) provides an open-source OS-independent reference implementation of the ACPI specification (HP Pavilion DV7 Battery) .

History

The first revision of the ACPI specification was released in December 1996 supporting 16 and 32-bit addressing spaces. It wasn't until August 2000 that ACPI received 64-bit address support as well as support for multiprocessor workstations and servers with revision 2.0. In September 2004, revision 3.0 gave the ACPI specification support for SATA connectors, PCI Express bus, >256 multiprocessor support, ambient light sensors and user presence devices, as well as extending the Thermal model beyond the previous processor centric support (ACER TRAVELMATE 2410 battery) .

The latest of the major publications is that of revision 4.0. Released in June 2009, the 4.0 specification added many new features to the design; most notable are USB 3.0 support, logical processor idling support, and x2APIC support.

Motherboard

A motherboard is the central printed circuit board (PCB) in many modern computers and holds many of the crucial components of the system, while providing connectors for other peripherals. The motherboard is sometimes alternatively known as the main board, system board, or, on Apple computers, the logic board.It is also sometimes casually shortened to mobo (Dell XPS M1210 Battery) .

History

Prior to the advent of the microprocessor, a computer was usually built in a card-cage case or mainframe with components connected by a backplaneconsisting of a set of slots themselves connected with wires; in very old designs the wires were discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The Central Processing Unit, memory and peripherals were housed on individual printed circuit boards which plugged into the backplane (Dell Studio XPS 1340 Battery) .

During the late 1980s and 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard (see below). In the late 1980s, motherboards began to include single ICs (called Super I/O chips) capable of supporting a set of low-speed peripherals: keyboard, mouse, floppy disk drive, serial ports, and parallel ports (Dell Studio XPS 1640 Battery) .

As of the late 1990s, many personal computer motherboards supported a full range of audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer graphics typically retained only the graphics card as a separate component (Dell Vostro 1710 Battery) .

The early pioneers of motherboard manufacturing were Michronics, Mylex, AMI, DTK, Hauppauge, Orchid Technology, Elitegroup, DFI, and a number of Taiwan-based manufacturers.

The most popular computers such as the Apple II and IBM PC had published schematic diagrams and other documentation which permitted rapid reverse-engineering and third-party replacement motherboards (ASUS EEE PC900 battery) .

Usually intended for building new computers compatible with the exemplars, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment.

The term mainboard is archaically applied to devices with a single board and no additional expansions or capability (Dell RM791 battery) .

In modern terms this would includeembedded systems and controlling boards in televisions, washing machines, etc. A motherboard specifically refers to a printed circuit with the capability to add/extend its performance.

Overview

A motherboard, like a backplane, provides the electrical connections by which the other components of the system communicate, but unlike a backplane, it also connects the central processing unit and hosts other subsystems and devices (Sony VGP-BPS13 battery) .

A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables, although in modern computers it is increasingly common to integrate some of these peripherals into the motherboard itself (Sony VGP-BPL9 battery) .

An important component of a motherboard is the microprocessor's supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard (Sony VGP-BPL11 battery) .

Modern motherboards include, at a minimum:

• sockets (or slots) in which one or more microprocessors may be installed
• slots into which the system's main memory is to be installed (typically in the form of DIMM modules containing DRAM chips)
• a chipset which forms an interface between the CPU's front-side bus, main memory, and peripheral buses (Sony VGP-BPL15 battery)
• non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system's firmware or BIOS
• a clock generator which produces the system clock signal to synchronize the various components
• slots for expansion cards (these interface to the system via the buses supported by the chipset)
• power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards (Dell Inspiron E1505 battery) .

The Octek Jaguar V motherboard from 1993.This board has 6 ISA slots but few onboard peripherals, as evidenced by the lack of external connectors.

Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as PS/2 connectors for a mouse and keyboard (Dell Latitude E6400 battery) .

Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr. Additional peripherals such as disk controllers and serial ports were provided as expansion cards (HP Pavilion dv6000 Battery) .

Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat.

CPU sockets

Main article: CPU socket

A CPU socket or slot is an electrical component that attaches to a printed circuit board (PCB) and is designed to house a CPU (also called a microprocessor) (Sony Vaio VGN-FZ31S battery) .

It is a special type of integrated circuit socket designed for very high pin counts. A CPU socket provides many functions, including a physical structure to support the CPU, support for a heat sink, facilitating replacement (as well as reducing cost), and most importantly, forming an electrical interface both with the CPU and the PCB (Sony Vaio VGN-FZ31S battery) .

CPU sockets can most often be found in most desktop and server computers (laptops typically use surface mount CPUs), particularly those based on the Intel x86 architecture on the motherboard. A CPU socket type and motherboard chipset must support the CPU series and speed.

Integrated peripherals

Block diagram of a modern motherboard, which supports many on-board peripheral functions as well as several expansion slots (Hp pavilion dv6000 battery) .

With the steadily declining costs and size of integrated circuits, it is now possible to include support for many peripherals on the motherboard. By combining many functions on one PCB, the physical size and total cost of the system may be reduced; highly integrated motherboards are thus especially popular in small form factor and budget computers (Sony VGN-FW11S Battery) .

For example, the ECS RS485M-M, a typical modern budget motherboard for computers based on AMD processors, has on-board support for a very large range of peripherals (Sony VGP-BPS13A/B Battery) :

• disk controllers for a floppy disk drive, up to 2 PATA drives, and up to 6 SATA drives (including RAID 0/1 support)
• integrated ATI Radeon graphics controller supporting 2D and 3D graphics, with VGA and TV output
• integrated sound card supporting 8-channel (7.1) audio and S/PDIF output
• Fast Ethernet network controller for 10/100 Mbit networking (Sony VGP-BPS13B/B Battery)
• USB 2.0 controller supporting up to 12 USB ports
• IrDA controller for infrared data communication (e.g. with an IrDA-enabled cellular phone or printer)
• temperature, voltage, and fan-speed sensors that allow software to monitor the health of computer components

Expansion cards to support all of these functions would have cost hundreds of dollars even a decade ago; however, as of April 2007 such highly integrated motherboards are available for as little as $30 in the USA (Toshiba Satellite P10 Battery) .

Peripheral card slots

A typical motherboard of 2009 will have a different number of connections depending on its standard.

A standard ATX motherboard will typically have one PCI-E 16x connection for a graphics card, two conventional PCI slots for various expansion cards, and one PCI-E 1x (which will eventually supersede PCI) (SONY VAIO VGN-FZ210CE Battery) .

A standard EATX motherboard will have one PCI-E 16x connection for a graphics card, and a varying number of PCI and PCI-E 1x slots. It can sometimes also have a PCI-E 4x slot. (This varies between brands and models.)

Some motherboards have two PCI-E 16x slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI(for Nvidia) and Crossfire (for ATI) (SONY VAIO VGN-FZ38M Battery) .

These allow 2 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming and video editing.

As of 2007, virtually all motherboards come with at least four USB ports on the rear, with at least 2 connections on the board internally for wiring additional front ports that may be built into the computer's case (SONY VAIO VGN-FZ31z Battery) .

Ethernet is also included. This is a standard networking cable for connecting the computer to a network or a modem. A sound chip is always included on the motherboard, to allow sound output without the need for any extra components. This allows computers to be far more multimedia-based than before. Some motherboards have their graphics chip built into the motherboard rather than needing a separate card. A separate card may still be used (SONY VAIO VGN-FZ31E Battery) .

Temperature and reliability

Main article: Computer cooling

Motherboards are generally air cooled with heat sinks often mounted on larger chips, such as the Northbridge, in modern motherboards. If the motherboard is not cooled properly, it can cause the computer to crash. Passive cooling, or a single fan mounted on the power supply, was sufficient for many desktop computer CPUs until the late 1990s; since then, most have required CPU fansmounted on their heat sinks, due to rising clock speeds and power consumption (SONY VAIO VGN-FZ31J Battery) .

Most motherboards have connectors for additional case fans as well. Newer motherboards have integrated temperature sensors to detect motherboard and CPU temperatures, and controllable fan connectors which the BIOS or operating system can use to regulate fan speed. Some computers (which typically have high-performance microprocessors, large amounts of RAM, and high-performance video cards) use a water-cooling system instead of many fans (SONY VAIO VGN-FZ31M Battery) .

Some small form factor computers and home theater PCs designed for quiet and energy-efficient operation boast fan-less designs. This typically requires the use of a low-power CPU, as well as careful layout of the motherboard and other components to allow for heat sink placement (SONY VAIO VGN-FZ31B Battery) .

A 2003 study found that some spurious computer crashes and general reliability issues, ranging from screen image distortions to I/O read/write errors, can be attributed not to software or peripheralhardware but to aging capacitors on PC motherboards. Ultimately this was shown to be the result of a faulty electrolyte formulation (SONY VGP-BPS13 Battery) .

For more information on premature capacitor failure on PC motherboards, see capacitor plague.

Motherboards use electrolytic capacitors to filter the DC power distributed around the board. These capacitors age at a temperature-dependent rate, as their water based electrolytes slowly evaporate. This can lead to loss of capacitance and subsequent motherboard malfunctions due to voltage instabilities (Dell Precision M70 Battery) .

While most capacitors are rated for 2000 hours of operation at 105 °C,their expected design life roughly doubles for every 10 °C below this. At 45 °C a lifetime of 15 years can be expected. This appears reasonable for a computer motherboard. However, many manufacturers have delivered substandard capacitors, which significantly reduce life expectancy. Inadequate case cooling and elevated temperatures easily exacerbate this problem. It is possible, but tedious and time-consuming, to find and replace failed capacitors on PC motherboards (Acer Aspire One battery) .

Form factor

Main article: Comparison of computer form factors

microATX form factor motherboard

Motherboards are produced in a variety of sizes and shapes called computer form factor, some of which are specific to individual computer manufacturers (Toshiba Satellite L305 Battery) .

However, the motherboards used in IBM-compatible commodity computers have been standardized to fit various case sizes. As of 2007, most desktop computer motherboards use one of these standard form factors—even those found in Macintosh and Sun computers, which have not traditionally been built from commodity components. The current desktop PC form factor of choice is ATX (Toshiba Satellite M65 battery) .

A case's, motherboard and PSU form factor must all match, though some smaller form factor motherboards of the same family will fit larger cases. For example, an ATX case will usually accommodate a microATX motherboard.

Laptop computers generally use highly integrated, miniaturized and customized motherboards. This is one of the reasons that laptop computers are difficult to upgrade and expensive to repair (Toshiba Satellite T4900 Battery) .

Often the failure of one laptop component requires the replacement of the entire motherboard, which is usually more expensive than a desktop motherboard due to the large number of integrated components.

Bootstrapping using the BIOS

Main article: booting

Motherboards contain some non-volatile memory to initialize the system and load an operating system from some external peripheral device (Toshiba PA3399U-2BRS battery) .

Microcomputers such as the Apple II and IBM PC usedROM chips, mounted in sockets on the motherboard. At power-up, the central processor would load its program counter with the address of the boot ROM and start executing ROM instructions, displaying system information on the screen and running memory checks, which would in turn start loading memory from an external or peripheral device (disk drive) (Dell Latitude E6400 battery) .

If none is available, then the computer can perform tasks from other memory stores or display an error message, depending on the model and design of the computer and version of the BIOS.

Most modern motherboard designs use a BIOS, stored in an EEPROM chip soldered to the motherboard, to bootstrap the motherboard (Toshiba Satellite A200 Battery) .

(Socketed BIOS chips are widely used, also.) By booting the motherboard, the memory, circuitry, and peripherals are tested and configured. This process is known as a computer Power-On Self Test (POST) and may include testing some of the following devices:

• floppy drive
• network controller (Toshiba Satellite 1200 Battery)
• CD-ROM drive
• DVD-ROM drive
• SCSI hard drive
• IDE, EIDE, or SATA hard disk
• External USB memory storage device (Toshiba NB100 Battery)

Any of the above devices can be stored with machine code instructions to load an operating system or program.

Chipset

A chipset, PC chipset or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product (Toshiba Satellite M300 Battery) .

Computers

Diagram of a motherboard chipset

In computing, the term chipset is commonly used to refer to a set of specialized chips on a computer's motherboard or an expansion card. Inpersonal computers the first chipset for the IBM PC AT was the NEAT chipset by Chips and Technologies for the Intel 80286 CPU (Dell INSPIRON 1525 battery) .

Chipsets are the main controllers on the motherboard - they allow the CPU to interface with the various components and expansion cards installed .”

Based on Intel Pentium-class microprocessors, the term chipset often refers to a specific pair of chips on the motherboard: the northbridge and thesouthbridge (Dell Inspiron Mini 10 Battery) .

The northbridge links the CPU to very high-speed devices, especially main memory and graphics controllers, and the southbridge connects to lower-speed peripheral buses (such as PCI or ISA). In many modern chipsets, the southbridge actually contains some on-chip integrated peripherals, such as Ethernet, USB, and audio devices (Dell Latitude D830 Battery) .

A chipset is usually designed to work with a specific family of microprocessors. Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance.

The manufacturer of a chipset often is independent from the manufacturer of the motherboard. Current manufacturers of chipsets for PC-compatiblemotherboards include NVIDIA, AMD, VIA Technologies, SiS, Intel and Broadcom (Dell Studio 1735 Battery) .

Apple computers and Unix workstations from Sun, NeXT, SGI, and others have traditionally used custom-designed chipsets; now that Sun and Apple both have x86 processors in at least some of their lines of products, they have begun to use standard PC chipsets in some of their computers. Some server manufacturers also develop custom chipsets for their products (Dell Latitude D620 Battery) .

In the 1980s, Chips and Technologies, founded by Gordon Campbell, pioneered the manufacturing of chipsets for PC-compatible computers. Computer systems produced since then often share commonly used chipsets, even across widely disparate computing specialties. For example, theNCR 53C9x, a low-cost chipset implementing a SCSI interface to storage devices, could be found in Unix machines such as the MIPS Magnum, embedded devices, and personal computers (SONY VAIO VGN-FZ150E Battery) .

In home computers, game consoles and arcade game hardware of the 1980s and 1990s, the term chipset was used for the custom audio and graphics chips. Examples include the Commodore Amiga's Original Chip Set or SEGA's System 16 chipset (Dell Studio 1555 Battery , Dell Latitude D610 Battery).